Basically this entirely.
From a Horde point of view, sure they've had a whole Arc of Sylvanas being bad and the others coming to terms with their feelings about being a part of a genocide and massacre. That doesn't excuse them of their actions though and their participation.
Saurfang and the rest of the Horde were an active and eager part in the slaughter and massacre of innocents and children. Sylvanas flying away doesn't exonerate them of all responsibility and guilt. Anduin honouring them as heroes and patting them all on the back now, with no consequences for their actions, is insulting for the entire rest of the Alliance.
Rather than give poor ol' Saurfang a heroes send off (After Teldrassil having been his plan in the first place) the cinematic should have ended with the Alliance arresting his ass and being like "Great, Sylvanas is gone.. but you're still responsible for the deaths of thousands of Night Elve civilians so fuck you. Into jail you go! "
I think you're seriously over estimating Blizzards writing team. This is the same Blizzard that thought Tyrande and the NightElves had had their vengeance already, after scaring away Nathanos and not even being able to kill him. The same Blizzard that fridged the whole Night Elve race to help Horde character development. It's the same Blizzard that seems to think you can be an active part of a genocide but if you feel bad about it afterwards then that makes everything ok.
I am actually genuinely worried they're going to make Tyrande a future raid boss for not being rational and Blizzard will call her a warmongerer for not forgiving and thanking all the poor Hordies for the genocide of her people.